The subject invention relates generally to gas turbines. More particularly, the subject invention relates to fuel nozzles for gas turbine engines.
Gas turbines typically include a quantity of fuel nozzles (or swozzles) in a combustor section of the gas turbine. Each nozzle is a component having one or more passages for delivering a mixture of fuel and air to a combustion chamber for ignition. A fuel nozzle often includes a swirler to improve mixing of the fuel and air into a consistent, homogeneous mixture prior to ignition. The swirler includes a plurality of vanes extending from the nozzle and having an aerodynamic profile. The swirler vanes often include passages which provide fuel to fuel holes on a surface of the swirler vanes. As fuel exits the fuel holes, it mixes with fluid, typically air, passing the swirler vanes. The fuel holes are typically configured as straight holes connecting a fuel plenum in a swirler vane to the passage where the fuel mixes with air. The fuel holes configured as such typically inject the fuel substantially perpendicular to the passing air. When fuel is injected into the passing airflow, a jet-in-crossflow phenomena is created which results in the formation of a recirculation zone of low-velocity flow downstream of the injection hole, but substantially upstream of the combustion zone.
The recirculation zone is problematic, especially for highly-reactive, high-hydrogen fuels such as syngas, carbon-free syngas and hydrogen-natural gas blends. These fuels have much shorter blow-off or blow-out times than residence time of the fuel in the low-velocity recirculation zone, so if an ignition source is provided, any fuel in the recirculation zone may ignite and continue to burn near the swirler vane, damaging the fuel nozzle and possibly other components of the gas turbine.